tests: new test for mq qdiff command
`hg qdiff .' is supposed to work but it is currently broken.
This test should help us verify when it gets fixed.
Is there an error message when trying to diff non-existing files?
found: No such file or directory
not: No such file or directory
Is there an error message when trying to add non-existing files?
found: No such file or directory
not: No such file or directory